Slant hole drilling rig

ABSTRACT

A drilling mast is mounted on a support means which is pivotally mounted in an arcuate well formed in a drilling rig base structure whereby the mast may be tilted. A vertical selfsupporting setback tower is mounted on the base structure adjacent the well for racking lengths of drill pipe. An adjustable strut or tie member extends between the drilling mast and the setback tower for maintaining the drilling mast at a desired angle of inclination. A catwalk structure is pivotally connected to the drilling mast and movably coupled to an upper portion of the setback tower so that it will always be horizontal, regardless of the angle of the drilling mast relative to the tower. A pipe pullback mechanism is supported for movement between the drilling mast and tower for use in transferring drill pipe back and forth between the drilling mast and the setback tower.

United States Patent Selfe et a1. Mar. 21, 1972 [541 SLANT HOLE DRILLING RIG 721 Inventors: Richard J. Selle; Donald L. Bleyl, both of [22] Filed: Sept. 15, 1969 [21] Appl. No.: 858,043

[52] US. Cl ..175/85, 175/5 [51] Int. Cl ..E2lb 19/00 [58] Field olSearch ..l75/85,5; l73/40,41,44

[56] References Cited UNITED STATES PATENTS 2,999,549 9/1961 Stratton ..175/5 3,371,728 3/1968 Crooke et a]. ....l75/85 3,443,647 5/1969 Jenkins et a1. ..l75/85 3,464,507 9/1969 Alexander et a1 173/44 X 3,451,493 6/1969 Storm ....175/85 X 3,503,460 3/1970 Gadbois ..l75/5 c/o Pyramid Derrick and Equipment Co., PO. Box 40338, Houston, Tex. 77040 Anomey.lack W. Hayden and Richard E. Bee

[57] ABSTRACT A drilling mast is mounted on a support means which is pivotally mounted in an arcuate well formed in a drilling rig base structure whereby the mast may be tilted. A vertical selfsupporting setback tower is mounted on the base structure adjacent the well for racking lengths of drill pipe. An adjustable strut or tie member extends between the drilling mast and the setback tower for maintaining the drilling mast at a desired angle of inclination. A catwalk structure is pivotally connected to the drilling mast and movably coupled to an upper portion of the setback tower so that it will always be horizontal, regardless of the angle of the drilling mast relative to the tower. A pipe pullback mechanism is supported for movement between the drilling mast and tower for use in transferring drill pipe back and forth between the drilling mast and the setback tower.

21 Claims, 10 Drawing Figures Patented March 21, 1972 3,650,339

4 Sheets-Sheet 1 M Jana/d z. fi/y/ I, INVEN'I'ORI f By M u m Riclmnd/ Bea Patented March 21, 1972 7 3,650,339

4 Sheets-Sheet 2 f% fw INVENTIURJ' Junk Hand? Richard Bu,

Patented March 21, 1972 4 Sheets-Sheet 5 .J m wm m m H m 3 w n J 17 2 M Z A Y B Patented March 21, 1972 4 Sheets-Sheet 4 SLAN'I' HOLE DRILLING RIG BACKGROUND OF THE INVENTION This invention relates to drilling rigs for drilling boreholes into the earth. While not limited thereto, the invention is particularly useful in drilling oil and gas well boreholes.

It is sometimes desired to drill an oil or gas well into the earth at a slanted or oblique angle with respect to'the surface of the earth. One way of doing this is to use a tilted drilling mast for feeding the drill bit and drill pipe into the earth at the desired angle. When the mast is tilted, however, it becomes more difficult to transfer lengths of drill pipe from the drilling mast to a pipe storage rack and vice versa when making a trip for purposes of changing a worn bit or the like or for other reasons. Various solutions to this problem have been heretofore proposed. These prior proposals involve the use of structures which suffer from various disadvantages and drawbacks. Some are not very stable and cannot sustain very heavy wind loads. Some are of a rather bulky and cumbersome construction and are difficult to manipulate. Some are constructed in such a manner that the safety of the operating personnel is jeopardized.

One prior art patent is that to C. Jenkins et al., U.S. Pat. No. 3,443,647. However, this patent discloses a construction, which is objectionable for numerous reasons. For example, the catwalk between the mast and setback structure is not horizontal, but slopes which increases the hazards to personnel. Also, the setback tower is not self-supporting, which reduces the stability of the apparatus, and increases the structure necessary to support the tower. Additionally the drilling mast is surrounded on its sides by the catwalk and the catwalk is removably secured to the mast, so that the difiiculty and dangers of adjusting the mast to a different angle are apparent.

Drill pipe have long been stacked vertically in drilling rigs, as generally indicated in U.S. Pat. No. 3,443,647, and even in this patent no suitable means for conveying the pipe between the setback and drilling mast are shown.

SUMMARY or THE INVENTION It is an object of the invention, therefore, to provide a new and improved slant hole drilling rig having an improved form of construction, which is stable'and less hazardous to personnel.

It is another object of the invention to provide a new and improved slant hole drilling rig having better wind loading characteristics.

It is a further object of the invention to provide a new and improved slant hole drilling rig which is safer for the operating personnel.

In accordance with the invention, a slant hole drilling rig comprises a base structure and a drilling mast mounted .on a support which is received in an arcuate well in a base structure. The drilling rig also includes a setback tower mounted on the base structure adjacent the arcuate well and including pipe rack means for racking lengths of pipe. The drilling rig further includes catwalk means pivotally coupled to the drilling mast and slidably coupled to an upper portion of the setback tower. The drilling rig also includes pipe pullback means supported for the movement between the drilling mast and tower for transferring pipe between the drilling mast and the pipe rack means.

For a better understanding of the present invention,

together with other and further objects and features thereof,

reference is had to the following description taken in connection with the accompanying drawings, the scope of the invention being pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings:

FIG. 1 is an elevational view of a slant hole drilling rig constructed in accordance with the present invention;

FIG. 2 is an elevational view taken at right angles to, and along the line 2-2 of FIG. 1;

FIG. 3 is a plan view taken along section line 3-3 of FIG. 1;

FIG. 4 is an enlarged elevational view of a pipe pullback mechanism of the FIG. 1 drilling rig;

FIG. 5 is a partial plan view taken along section line 5-5 of FIG. 4; I

FIG. 6 shows a catwalk hanger structure used on the FIG. 1 drilling rig:

FIG. 7 is a side view of the FIG. 6 structure;

FIG. 8 is an enlarged view of a lower portion of the drilling mast structure of FIG. 1;

FIG. 9 is a partial plan view of the main deck of the FIG. 1 drilling rig; and

FIG. 10 is an enlarged view of the rat hole coupling structure ofFIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a slant hole drilling rig having a platform or base structure 10 supportinga primary working deck 11. The structure 10 is shown as supported by suitable support legs 10a in a water covered area; howeverit can as easily be used on land. A tiltable drilling mast 12 is pivotally mounted on the base structure 10 and a vertical setback tower 13 is mounted on the base structure l0 adjacent the drilling mast 12 and in line with the direction of pivoting thereof. The base structure 10 includes an arcuate well 14 formed by a cylindrical socket structure 14a for receiving a cylindrical support base 15 of the drilling mast 12. Rotation of the mast support base 15 in the arcuate well 14 enables the drilling mast 12 to be inclined at the desired angle, an angle of 30being the one illustrated in FIG. I. A series of coupling pin passages 15a enables the support base 15 to be locked at the desired angle, a locking pin being inserted into the appropriate one of the passages 1511 which is in alignment with a cooperating passage in an extension 10b of the base structure 10.

Secured to the mast support base 15 is a mast pedestal 16 to the upper end of which is releasably connected the remainder of the drilling mast 12. A rotary table 17 is mounted on the pivotal support base 15. Rotary table 17 is driven by drawworks 18, located on the working deck 11, by means of the usual drive chain which, for simplicity of illustration, is not shown in FIG. 1. The relatively large upper surface area 15b of the pivotal support base 15 enables other rig equipment, such as power tongs and the like, to be located thereon and, thus, to be maintained at the proper angle with respect to the drill pipe being run into the well bore.

Located within the confines of the drilling mast 12 is a traveling block 20 which is pivotally coupled to a dolly 21 which rides on a guide track 22 (FIG. 2) which is secured to the lower one ofthe inclined sides of the mast l2 and which extends most of the length thereof. Dolly 21 is shown to an enlarged scale in FIG. 8. Traveling block 20 is suspended from a crown block 23 by multiple loops of a hoisting'line 24, which line 24 leaves the crown block 23 by way of a direction changing sheave 25 and runs to the winch drum of the drawworks l8. Shown connected to the hook of the traveling block 20 in FIG. 1 is a swivel mechanism 26 to which is connected a drilling kelly 27 to the lower end of which is connected a joint of drill pipe 28. Pipe 28 is the upper joint of the drill string which extends downwardly into the borehole being drilled into the earth. Such pipe 28 passes through the rotary table 17 and into the borehole in the usual manner shown in FIG. 1.

The setback tower 13 is of a self-supporting construction and includes four primary spaced apart vertically extending frame members which are secured to the base structure 10 at four different points defining the four corners of a rectangle. This self-supporting construction reduces the bulkiness of the rig structure. The setback tower 13 includes a pipe rack structure 30 for racking the upper ends of vertically standing lengths of drill pipe 31 which are only partially shown in FIG. 1.

A mast hanger strut or tie member 32 is pivotally pinned at one end to the drilling mast 12 and at the other end to the setback tower 13, the latter connection being made by means of a coupling bracket 33 which is mounted on the setback tower 13. The hanger strut 32 is provided with a series of coupling pin receiving apertures 34 along the length thereof. Each aperture 34 is capable of receiving the coupling pin which is used with the coupling bracket 33. By selecting the appropriate one of the apertures 34, the drilling mast 12 can be further braced at the desired angle of inclination.

The drilling mast 12 is moved from one angular position to another by means of a mast raising ram mechanism 35 which is coupled between the lower side of the mast 12 and the base structure 10 of the drilling rig. The vertical position of the drilling mast 12 is indicated in outline form at 36 in'FIG. 1. Typical intermediate positions are indicated by center lines 37 and 38. The laydown position of the mast 12 is indicated in outline form at 39. This latter position is used when transporting the-drilling rig from one well site to another. In this position, the'right-hand legs of the upper portion of the mast 12 are disconnected from the mast pedestal 16.

In order to enable the drilling rig personnel to manipulate the drill pipe for purposes of transferring it from the setback tower 13 to the drilling mast 12 or vice versa when making a trip, there is provided a catwalk structure 40 which extends horizontally between a midposition on the drilling mast 12 and an upper position on the setback tower 13. As best seen in FIG. 3, the catwalk structure 40 includes a horizontal walkway 41 which extends between the mast 12 and tower 13 on one side of the pipe transfer path and a horizontal strut member 42 which extends between the mast 12 and tower 13 on the other side of the pipe transfer path. Drill pipe 28 is shown as being in the drilling mast 12, it being assumed that the pipe is to be pulled from the well bore and that swivel 26 and kelly 27 have been removed. The walkway structure 41 is pivotally pinned in a permanent manner to the drilling mast 12 at 43, while the strut member 42 is pivotally pinned in a permanent manner to mast 12 at 44 (FIG. 3). A walkway extension or access platform 45 is secured to the walkway structure 41 and extends into the confines of the drilling mast 12.

Suspended from the underside of the walkway structure 41 is a movable pipe pullback dolly 46. As indicated in the elevational view of FIG. 4, this dolly 46 rides on a pair of side-byside track members 47 which, as shown in FIG. 6, is mounted on a pair of side-by-side support beams 48 of the walkway structure 41. Beams 48 are tied to one another by means of end plates 49 and 50. The pullback dolly 46 includes appropriate support rollers 51 and side bearing rollers 52 for guiding it along the track members 47. The driving mechanism for driving the pullback dolly 46 includes cable rollers 53 and 54 rotatably mounted at the extremities of the track 47 and a drive cable 55 which is attached to the left-hand end of the dolly 46, extends to and passes over the left-hand cable roller 54, returns to and passes over the righthand cable roller 53 and then runs to and is connected to the right-hand end of the dolly 46. Cable 55 makes several loops around the roller 53 before it returns to the dolly 46. Cable roller 53 is powered by a reversible winch motor 56. Thus, operation of the motor 56 causes movement of the pullback dolly 46 along the track 47.

In addition to the dolly 46, the pipe pullback mechanism includes a pipe grabbing mechanism for grabbing the upper end of the pipe in the drilling mast 12. This pipe grabbing mechanism includes an arm member 57 which is pivotally coupled to the pullback dolly 46 and which, as indicated in FIG. 3, extends inwardly into the pipe transfer path intermediate the walkway 41 and the strut member 42. Secured to the outer end of the arm member 57 is a vertically extending post member 58. Pivotally coupled to the upper end of the post member 58 is a set of elevator jaws 59 for encircling and gripping the drill pipe to be transferred.

The brackets used for pinning the walkway structure 41 to the drilling mast 12 are indicated at 60 in FIGS. 4 and 5. Also, as indicated in FIG. 1, the walkway 41 may be provided with a handrail 61.

The setback tower ends of the walkway structure 41 and the strut member 42 are slidably supported by the setback tower 13 so that when the drilling mast 12 is raised to a higher position both the walkway structure 41 and the strut member 42 slide on through and out the other side of the setback tower 13. More particularly, the walkway structure 41 is hung below the pipe rack structure 30 by means of a hanger assembly 62 which, as indicated in FIGS. 1 and 3, is located at the rear of the pipe rack structure 30. The hanger assembly 62 is pinned to rearwardly extending brackets 63 which are mounted on a rearward extension of the pipe rack structure 30. An elevational view of the hanger assembly 62 is shown in FIG. 6 and a side view thereof in FIG. 7. As indicated in these figures, the hanger assembly 62 includes a pair of vertical side members 63 and 64 which is connected by a crossmember 65. A roller 66 is rotatably supported between the lower ends of the side members 63 and 64. The walkway structure 41 and more particularly the support beams 48 thereof ride on this roller 66, thus enabling the sliding movement of the walkway structure 41 when the drilling mast is moved to a difi'erent angular position. Pin receiving passages 67 at the upper ends of the side members 63 and 64 are adapted to receive the coupling pins which are used to couple the hanger assembly 62 to the brackets 63 on the pipe rack structure 30. Set screws 67a are provided for locking the walkway structure 41 in place after the positioning of the drilling mast 12 has been completed.

As indicated in FIGS. 2 and 3, the strut member 42 is hung from the rear of the pipe rack structure 30 in a similar manner by means of a further hanger assembly 68. This hanger assembly 68 is pinned to bracket members 69 which are, in turn, secured to a rearward extension of the pipe rack structure 30.

In order to ensure maximum safety for the operating personnel, it is desired that the walkway structure 41 always be in a horizontal position regardless of the angle of inclination of the drilling mast 12. In order to accomplish this purpose, it is necessary to provide means for raising and lowering the setback tower end of the catwalk structure 40. In the present embodiment, this is accomplished by enabling an upward or downward adjustment of the position of the pipe rack structure 30. To this end, the pipe rack structure 30 is provided with four sets of laterally extending coupling brackets 70 (FIG. 3) which cooperate with a series of coupling pin passages 71 (FIG. 2) in each of four vertical frame member segments 72 of the setback tower structure 13 for purposes of enabling the pipe rack structure 30 to be pinned to the setback tower 13 at any one of several different vertical positions. The coupling pins which pass through the brackets 70 and passages 71 are indicated at 73 in FIG. 3. A second vertical position for the pipe rack structure 30 is indicated in outline form at 300 in FIG; 2. The coupling pin passages 71 are spaced in a manner which complements the spacing of the pin receiving apertures 34 in the mast hanger strut 32 such that for each aperture 34 in the hanger strut 32 there is a corresponding passage 71 which ,will provide, a horizontal positioning for the catwalk structure 40. An auxiliary hand-operated chain hoist 74 and hoisting chain 74aare located on the setback tower 13 for raising and loweringthe pipe rack structure 30 to change its position, the pins 73 being removed at such time.

Referring now to FIG. 8, there is shown a lower pipe positioner mechanism 75 which is located on the drilling mast 12 a short distance above the mast pedestal 16 and which is used for manipulating the lower end of a length of drill pipe either before it is connected to or after it is disconnected from the remainder of the pipe string in the well bore. This pipe positioner mechanism 75 includes a pair of side-by-side pipe positioning arms 76 having a pipe engaging roller 77 rotatably supported between the lower ends thereof. The upper ends of arms 76 are pivotally pinned intermediate the side rails 22a and 22b of the traveling block guide track 22 by pin 78. A crank arm 79 is fastened to the upper ends of the pipe positioning arms 76 and at right angles thereto, such arm 79 also pivoting about the pin 78. A hydraulic ram mechanism 80 is pivotally coupled to a support bracket structure 81 which is secured to the guide track 22. A piston rod 82 of the ram 80 is pivotally connected to the outer end of the crank arm 79.

The solid line construction in FIG. 8 shows the pipe positioner mechanism 75 in its retracted position. When the ram mechanism 80 is energized the piston rod 82 is extended to drive the crank arm 79 in a downward direction, thus driving the lower ends of the pipe positioning arms 76 in an outwardly and upwardly curving arc. Different extended positions for the pipe positioning arms 76 and the pipe engaging roller 77 are shown in outline form in FIG. 8, the lower end of a length of drill pipe being indicated in outline form at 84 and 84 for these extended positions. Except for the particular case described hereinafter, the pipe positioner mechanism 75 is not operated when the traveling block 20 is in the position shown in FIG. 8. This lower position of the traveling block 20 is used to illustrate the relationship between the traveling block dolly 21 and the pipe positioner mechanism 75. As further seen in FIG. 8, the swivel mechanism 26 and drilling kelly 27 of FIG. 1 have been removed and replaced by a pair of side-by-side elevator links 85 and a pipe elevator 86. Such items are used when pulling pipe out of or running it back into the subsurface borehole.

FIG. 8 further shows the upper end of a tiltable mouse hole 87. As there indicated, the mouse hole 87'includes a mouse hole pipe 87a having a sleeve 87b mounted on the upper end thereof. Such sleeve 87b is pivotally pinned by pins 88 to brackets 89 mounted on a support beam 90 forming part of the pivotal support base of the mast 12. As indicated in FIG. 1, the mouse hole pipe 87a extends downwardly from the mast support base 15 and into the water below the drilling rig base structure 10. A joint of drill pipe 91 is shown in outline form as being positioned in the mouse hole 87.

Referring now to FIG. 9, there is shown the location of a rat hole 92 for use with the present drilling rig. The upper end of this rat hole 92 is secured to the pivotal support base 15 of the drilling mast 12 by means of a gimbal mechanism which is shown to an enlarged scale in FIG. 10. As there indicated, the rat hole 92 includes a rat hole pipe 93 pivotally coupled to a first gimbal ring 94 by pivot pins 95. Gimbal ring 94 is, in turn, pivotally coupled to a second gimbal ring 96 by way of pivot pins 97, these pins 97 lying on an axis at right angles to the axis of the first pivot pins 95. The outer gimbal ring 96 is secured to the drilling mast support base 15. This gimballed coupling mechanism for the rat hole 92 enables the downwardly extending rat hole pipe 93 to tilt in any direction when the drilling kelly and swivel are being inserted into or withdrawn from the rat hole 92.

As shown in FIG. 1, the inclined drilling mast 12 has mounted thereon at a position near the longitudinal midpoint thereof an upper pipe positioner mechanism 98. This upper mechanism 98 includes an angular positioning member 99 which is pivotally pinned to the mast 12 and which extends inwardly through an opening in the traveling block guide track 22 for purposes of engaging the drilling kelly 27. The cylinder of a hydraulic piston mechanism 100 is pivotally connected at a lower point to the mast 12, while the piston rod of such mechanism is pivotally connected to the elbow of the positioning member 99. When the piston rod of piston mechanism 100 is retracted, the positioning member 99 is moved inwardly to engage and support the drilling kelly 27. Such positioner mechanism 98 is used, when necessary, to center the lower end of the drilling kelly 27 within the mast 12 when a new length of drill pipe is being added to the drill string during the drilling of the earth borehole.

In use, the pipe pullback dolly 46 on the catwalk structure 40 and the lower pipe positioner 75 near the lower end of the drilling mast 12 are used for transferring pipe back and forth between the drilling mast 12 and the setback tower 13 when pulling the drill pipe out of the earth borehole for purposes of changing a worn bit or the like and thereafter running the drill pipe back into the borehole. During such operations, the elevator links 85 and pipe elevator 86 shown in FIG. 8 are used, the swivel 26 and kelly 27 having been disconnected from the drill string and stored in the rat hole 92.

When pulling the drill string from the borehole, the pipe elevator 86 (FIG. 8 is clamped onto the upper end of the length of drill pipe extending out of the rotary table 17 and the traveling block 20 is then raised until the lower end of such pipe length is a short distance above the rotary table 17. This completely withdrawn length of pipe is then disconnected from the next lower length of pipe. The pullback dolly 46 is moved adjacent the drilling mast 12 and the elevator jaws 59 located at the end of the dolly arm assembly are clamped around the upper end of this length of drill pipe and the pipe elevator 86 is unfastened and removed from the pipe. The pipe positioner 75 is then operated to move the lower end of this length of drill pipe toward the setback tower 13 in the manner indicated by the outline positions of FIG. 8. At the same time, the pullback dolly 46 is operated to move the upper end of the pipe toward the setback tower 13. The lower end of the pipe is placed on the deck floor at the bottom of the setback tower 13 and the pullback dolly 46 is operated to move the upper end of the pipe into one of the racks on the pipe rack structure 30.

Subsequent lengths of the drill pipe are removed from the borehole and moved from the drilling mast 12 to the setback tower 13 in this same manner until all of the pipe has been removed from the borehole. At this time, the worn drill bit can be replaced or whatever other operation it was desired to perform can be performed.

When it is desired to run the drill string back into the borehole, the reverse type of operation is performed. Lengths of drill pipe are transferred one at a time from the setback tower 13 to the drilling mast 12, each length being connected in an endwise manner to the preceding length and then lowered into the borehole by the traveling block 20.

The lower pipe positioner mechanism 75 can also be used to close the pipe elevator 86 (FIG. 8). This is accomplished by operating the ram mechanism to drive'the roller 77 against the elevator links 85. This, in turn, closes the jaws of the elevator 86. This lower pipe positioner mechanism 75 can also be used to move the drilling kelly 27 (FIG. 1) when attaching the lower end of same to the next length of drill pipe stored in the mouse hole 87 (FIG. 8) during the drilling of the earth borehole.

The permanent coupling of the catwalk structure 40 to the drilling mast 12 and the provision of means for enabling the catwalk structure 40 to slide through the setback tower 13 simplify the procedure for changing the angle of inclination of the drilling mast 12 and improve the safety of such procedure. Among other things, it is not necessary for a member of the drilling crew to climb the inclined drilling mast for purposes of disconnecting the catwalk structure when it is desired to change the angle. This manner of construction also improves the winding loading characteristics of the structure.

While there has been described what is at present considered to be a preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A slant hole drilling rig for drilling boreholes into the earth comprising:

a. a base structure;

b. an arcuate well formed in the base structure;

c. a setback tower mounted on the base structure adjacent the well in said base structure and including pipe rack meansfor racking lengths of pipe;

d. support means pivotally mounted in the well;

e. a drilling mast mounted on said support means whereby said mast may be tilted relative to said tower;

f. catwalk means pivotally coupled to the drilling mast and slidably coupled to said tower; and

g. pipe pullback means movable between said tower and drilling mast for moving pipe between said mast and tower.

2. The invention of claim 1 wherein said pipe pullback means is movably supported by said catwalk means.

3. A slant hole drilling rig in accordance with claim 1 wherein the setback tower is located in line with the direction of pivoting of the drilling mast and the rig includes strut means adjustably coupled between the drilling mast and the setback tower for maintaining the drilling mast in a desired inclined position.

4. A slant hole drilling rig in accordance with claim 1 wherein the catwalk means includes only a single walkway extending between the drilling mast and the setback tower, such walkway being located on one side of the path followed by the pipe when transferred from the drilling mast to the pipe rack means.

5. A slant hole drilling rig in accordance with claim 1 wherein the pipe pullback means includes pipe grabbing means for grabbing the upper portion of a length of pipe situated within the drilling mast.

6. A slant hole drilling rig in accordance with claim 1 wherein the catwalk means includes a walkway structure extending between the drilling mast and the setback tower and located on one side of the path followed by the pipe when transferred from the drilling mast to the pipe rack means and wherein the pipe pullback means is movably supported by the walkway structure and includes pipe grabbing means which extends into the pipe transfer path for grabbing the upper portion of a length of pipe.

7. A slant hole drilling rig in accordance with claim 1 wherein a rotary table is supported on said support means.

8. A slant hole drilling rig in accordance with claim 1 wherein a mouse hole pipe is pivotally coupled to said support means and extending downwardly therefrom.

9. A slant hole drilling rig in accordance with claim 1 and including a rat hole pipe for storing a drilling kelly when not in use and gimbal means for coupling the rat hole pipe to said support means.

10. A slant hole drilling rig in accordance with claim 1 and including a hydraulic pipe positioner carried by the drilling mast near the longitudinal midpoint thereof and operable for centering the drilling kelly within the mast structure when a new length of drill pipe is being added to the drill string during the drilling of the borehole.

11. A slant hole drilling rig in accordance with claim 1 wherein the setback tower includes means for adjusting the elevation of the setback tower end of the catwalk means for maintaining the catwalk means in a horizontal position when the angle of inclination of the drilling mast is changed.

12. A slant hole drilling rig in accordance with claim 11 wherein the means for adjusting the elevation of the setback tower end of the catwalk means includes a pipe rack frame structure adapted for vertical movement with respect to the setback tower structure, locking means for locking the pipe rack frame structure to the setback tower structure at different elevations and hanger means attached to the pipe rack frame structure for slidably supporting the setback tower end of the catwalk means.

13. A slant hole drilling rig in accordance with claim 1 wherein the pipe pullback means includes track means extending most of the length of the catwalk means and secured thereto, a dolly movably supported by such track means, driving means for moving the dolly along the track means and pipe grabbing means coupled to the dolly and extending therefrom for grabbing the upper portion of a length of pipe situated within the drilling mast.

14. Aslant hole drilling rig in accordance with claim 13 wherein the driving means includes roller means located near the two extremities of the track means, cable means looped over the roller means and attachedto the forward and rearward ends of the dolly and motor means for driving one of the roller means.

15. A slant hole drilling rig in accordance with claim 1 wherein the setback tower is of a self-supporting construction.

16. A slant hole drilling rig in accordance with claim 15 wherein the setback tower includes four spaced apart vertically extending frame members which are secured to the base structure at four different locations thereon.

17. A slant hole drilling rig in accordance with claim 1.

wherein the well in said base structure includes a cylindrical socket structure and the drilling mast includes a cylindrical bottom structure seated in the socket structure for enabling the mast to be tilted at different angles with respect to a vertical axis.

18. A slant hole drilling rig in accordance with claim 17 wherein the rig includes a ram mechanism coupled between the base structure and the drilling mast for positioning the drilling mast at different inclined positions.

19. A slant hole drilling rig in accordance with claim 1 and including a hydraulic pipe positioner supported near the lower end of the drilling mast and operable for moving the lower end of a disconnected length of pipe out of the drilling mast and toward the setback tower.

20. A slant hole drilling rig in accordance with claim 19 wherein the hydraulic pipe positioner includes a pipe ejector arm pivotally coupled to the drilling mast structure on the side farthest removed from the setback tower and a hydraulic ram mechanism coupled between the drilling mast structure and the pipe ejector arm and operable for moving a free end of such arm away from the drilling mast structure and toward the setback tower.

21. A slant hole drilling rig for drilling boreholes into the earth comprising:

a. a base structure;

b. a support base pivotally mounted on the base structure;

c. a drilling mast pivotally mounted on the support base;

d. a setback. tower mounted on the base structure adjacent the support base and including pipe rack means for racking lengths of pipe;

e. a rat hole pipe for storing a drilling kelly; and

f. gimbal means for coupling the upper end of the rat hole pipe to the support base. 

1. A slant hole drilling rig for drilling boreholes into the earth comprising: a. a base structure; b. an arcuate well formed in the base structure; c. a setback tower mounted on the base structure adjacent the well in said base structure and including pipe rack means for racking lengths of pipe; d. support means pivotally mounted in the well; e. a drilling mast mounted on said support means whereby said mast may be tilted relative to said tower; f. catwalk means pivotally coupled to the drilling mast and slidably coupled to said tower; and g. pipe pullback means movable between said tower and drilling mast for moving pipe between said mast and tower.
 2. The invention of claim 1 wherein said pipe pullback means is movably supported by said catwalk means.
 3. A slant hole drilling rig in accordance with claim 1 wherein the setback tower is located in line with the direction of pivoting of the drilling mast and the rig includes strut means adjustably coupled between the drilling mast and the setback tower for maintaining the drilling mast in a desired inclined position.
 4. A slant hole drilling rig in accordance with claim 1 wherein the catwalk means includes only a single walkway extending between the drilling mast and the setback tower, such walkway being located on one side of the path followed by the pipe when transferred from the drilling mast to the pipe rack means.
 5. A slant hole drilling rig in accordance with claim 1 wherein the pipe pullback means includes pipe grabbing means for grabbing the upper portion of a length of pipe situated within the drilling mast.
 6. A slant hole drilling rig in accordance with claim 1 wherein the catwalk means includes a walkway structure extending between the drilling mast and the setback tower and located on oNe side of the path followed by the pipe when transferred from the drilling mast to the pipe rack means and wherein the pipe pullback means is movably supported by the walkway structure and includes pipe grabbing means which extends into the pipe transfer path for grabbing the upper portion of a length of pipe.
 7. A slant hole drilling rig in accordance with claim 1 wherein a rotary table is supported on said support means.
 8. A slant hole drilling rig in accordance with claim 1 wherein a mouse hole pipe is pivotally coupled to said support means and extending downwardly therefrom.
 9. A slant hole drilling rig in accordance with claim 1 and including a rat hole pipe for storing a drilling kelly when not in use and gimbal means for coupling the rat hole pipe to said support means.
 10. A slant hole drilling rig in accordance with claim 1 and including a hydraulic pipe positioner carried by the drilling mast near the longitudinal midpoint thereof and operable for centering the drilling kelly within the mast structure when a new length of drill pipe is being added to the drill string during the drilling of the borehole.
 11. A slant hole drilling rig in accordance with claim 1 wherein the setback tower includes means for adjusting the elevation of the setback tower end of the catwalk means for maintaining the catwalk means in a horizontal position when the angle of inclination of the drilling mast is changed.
 12. A slant hole drilling rig in accordance with claim 11 wherein the means for adjusting the elevation of the setback tower end of the catwalk means includes a pipe rack frame structure adapted for vertical movement with respect to the setback tower structure, locking means for locking the pipe rack frame structure to the setback tower structure at different elevations and hanger means attached to the pipe rack frame structure for slidably supporting the setback tower end of the catwalk means.
 13. A slant hole drilling rig in accordance with claim 1 wherein the pipe pullback means includes track means extending most of the length of the catwalk means and secured thereto, a dolly movably supported by such track means, driving means for moving the dolly along the track means and pipe grabbing means coupled to the dolly and extending therefrom for grabbing the upper portion of a length of pipe situated within the drilling mast.
 14. A slant hole drilling rig in accordance with claim 13 wherein the driving means includes roller means located near the two extremities of the track means, cable means looped over the roller means and attached to the forward and rearward ends of the dolly and motor means for driving one of the roller means.
 15. A slant hole drilling rig in accordance with claim 1 wherein the setback tower is of a self-supporting construction.
 16. A slant hole drilling rig in accordance with claim 15 wherein the setback tower includes four spaced apart vertically extending frame members which are secured to the base structure at four different locations thereon.
 17. A slant hole drilling rig in accordance with claim 1 wherein the well in said base structure includes a cylindrical socket structure and the drilling mast includes a cylindrical bottom structure seated in the socket structure for enabling the mast to be tilted at different angles with respect to a vertical axis.
 18. A slant hole drilling rig in accordance with claim 17 wherein the rig includes a ram mechanism coupled between the base structure and the drilling mast for positioning the drilling mast at different inclined positions.
 19. A slant hole drilling rig in accordance with claim 1 and including a hydraulic pipe positioner supported near the lower end of the drilling mast and operable for moving the lower end of a disconnected length of pipe out of the drilling mast and toward the setback tower.
 20. A slant hole drilling rig in accordance with claim 19 wherein the hydraulic pipe positioner includes a pipe ejector arm pivotally coupled to the drilling mast struCture on the side farthest removed from the setback tower and a hydraulic ram mechanism coupled between the drilling mast structure and the pipe ejector arm and operable for moving a free end of such arm away from the drilling mast structure and toward the setback tower.
 21. A slant hole drilling rig for drilling boreholes into the earth comprising: a. a base structure; b. a support base pivotally mounted on the base structure; c. a drilling mast pivotally mounted on the support base; d. a setback tower mounted on the base structure adjacent the support base and including pipe rack means for racking lengths of pipe; e. a rat hole pipe for storing a drilling kelly; and f. gimbal means for coupling the upper end of the rat hole pipe to the support base. 